Floating valves for shock absorbers



Aug. 10, 1965 3,199,636 CHRlSTlAN-MARlE-LUClEN-LOUIS BOURCIER DE CARBONFLOATING VALVES FOR SHOCK ABSORBERS Original Filed 001.. 9, 1962INVENTOR ATTOR NEYS United States Patent 3,199,636 FLGATHQG VALVE EGRHCK ABSQRBERS Christian-Marie-Lucien-Lonis Eourcier do Carlson, 64 Blvd.Maurice Barres, Nenilly-sunseine, France Continuation oi applicationSer. No. 229,386, 0st. 9, 1962. This application Apr. 25, 1963, Ser. No.275,7s7

t'llaims priority, application France, Apr. 26, 1962, 895,729 7 Claims.(Cl. 188-95) This application is a continuation of my ec-pendingapplication Serial No. 229,386, filed October 9, 1962, now forfeited.

This invention relates to shock absorbers and more particularly to shockabsorbers of the reciprocating directacting, piston-and-cylinder type,and has to do primarily with the piston valving.

The general object of the invention is to provide a novel and improvedvalve system for shock absorber pistons, in which the control of theflow of the damping fluid is more precise, and this without increasingthe liability of the valve parts to fatigue and fracture.

Pistons of this general nature are already known, as including a clackvalve comprising a thin annular disc or wafer or a packet of such discs,disposed between two seating ledges, the inner circular edge of theannular disc cooperating with one of the seats against which the surfaceof the disc rests, and the outer peripheral edge 01 the annular disccooperating with the other seat against which the opposite face rests.In such pistons a single valve is thus employed for controlling theoperation in both directions.

Not only are the discs in this type of valve not subjected to a housingor shrouding effect at any point, but they are not fixed at any point,which justifies the appelation floating clack valves. Moreover, thesmall shock effects which manifest themselves at very high frequencies,for example when a vehicle employing the shock absorber is travellingover paving stones, are eliminated, which of course improves the comfortof the ride.

In devices of this type, the action of the annular clack valve is notthe same in both directions, the section of the opening affording thepassage of the damping liquid being determined not only by thedisplacement of the clack valve, but also by the diameters, which arenot the same in operations in the two directions of movement. it hasbeen found from experience that to achieve a suitable value for thepressure ratios for the two directions of operation, the selection ordetermination of the two diameters does not by itself permit theobtaining of satisfactory results.

In its preferred embodiments, the invention contemplates the provisionof a piston, or other partition or separator, which has an annularcavity in one or the other of its opposite faces, and a plurality offree openings or passageways leading from the bottom of said cavitythrough the opposite face or" the piston.

Thin flexible resilient annular valve discs comprise the only movablevalve elements and one or more of these are disposed within the cavity,and fixed circular ledges are formed or otherwise provided on theoppositely facing imier and outer circular walls of the cavity forseating the discs. For purposes of use more particularly in a vehicularsuspension shock absorber, the ledge on the inner wall supports theinward margin of the discs against movement outwardly of the cavity andthe ledge on the outer wall forms an abutment or seat for the outwardmargin of the discs and limits its movement inwardly of the cavity.

The present invention therefore relates to improvements in devices ofthis type and is characterized principally s arter-uteri A 10, 1965 bythe fact that at the outlet of the passage or clearance existing betweenthe inside peripheral edge of the clack valve and its support, isdisposed an obstacle or throttling means comprising a part forming aprojection or juttingout in relation to the support, on the entireperiphery of a portion thereof, so as to increase the resistance of thepassage of damping liquid at this part of the valving.

In particular, this jutting or projecting part can be partially orwholly in the form of a surface of revolution and of a diameterprogressively decreasing from the valve disc support. For example, thejutting surface can be substantially conical so as to offer to thepassage of the liquid a variable and increasingly greater sectionproportionate to the degree of bending of the valve under the pressureof the liquid.

Other objects and features of novelty, including the provision of aslight pre-tensioning of the discs and of a calibrated conical memberdisposed axially and concentrically of the discs, will be apparent fromthe following specification when read in connection with theaccompanying drawings in which certain embodiments of the invention areillustrated by way of example.

In the drawings:

FEGURE 1 isa bottom plan view of a piston embodying the principles ofthe invention; I

FIGURE 2 is a View in vertical section of the piston positioned forreciprocation within a cylinder as for enample in a shock absorberstructure, the valves of the piston being in closet. or idle position;

FIGURE 3 is a similar view of a piston to which a modified form of valveseating means is applied; the valve discs being in position to passfluid downwardly past the outward margin of the discs;

FIGURE 4 is a similar view of the same embodiment with the valves inposition to pass fluid upwardly past the inward margins of the discs;and

FIGURE 5 is a view in perspective of a valve seating element of amodified construction.

For examples of the type of shock absorbers to which the presentinvention is particularly applicable, reference is made to a number ofprior patents granted to the present applicant, among which may bementioned my French Patents 1,020,109, 1,073,454, 1,104,016 and1,185,696, and therefore there need only be illustrated in the presentapplication those portions of the entire installation which embody thenovelty of the present invention. Thus, in FIGURE 2 of the drawings, theshock absorber cylinder or casing is only tragmentarily illustrated at10 and an exemplary piston is indicated generally by the numeral 12. Thepiston rod 15 has an attenuated terminal portion 16, to the threaded endof which is screwed a retaining nut f.7. Against the shoulder 18 formedat the junction of portions 15 and 16 of the piston rod, there is seatedan annular supporting piece Ell.

Above this member is clamped the mairi body portion 21 of the pistonwhich has a dished upper surface 22 and a relatively deep annular cavity25 formed in its under surface. Communication between the cavity 25 andthe upper face of the piston is had through the series of verticalpassageways 2s.

The outer circular wall of the cavity 25 is comprised by the marginalskirt 28 of the piston and the inner wall is comprised in part by theprojecting or jutting peripheral edge portion 20A of the supportingelement 20.

Supporting element 20 is provided with a ledge 3.0 upon which rests theradially inward marginal portion 31 of the flexible resilient valve discelement or elements 32. As will be explained, the number of valve discsneeded in this particular novel arrangement is reduced over thatrequired in certain similar piston valving arrangements. Two discs areillustrated, for example, in

35 the present drawings and in some cases even a single disc wouldsuflice.

The outer marginal portion 33 of the discs underlies the bottom marginof the skirt 28 which in effect forms a reversed abutment ledge 35. Thediscs 32 are preferably applied to the ledges 30 and 35 under a veryslight initial stress, just enough to ensure that in their position ofrepose shown in FIGURE 2, they seat against the respective ledges. It isto be particularly noted that this positioning of the valving withoutany gripping of the margins upon either side, eliminates any rigidlysupported cantilever arrangement which has characterized certain priordevices of this type. At the same time the discs are normally held incentered position at the inner edges rather than at the outer edgesthereof.

In FIGURES 3 and 4 of the drawings, there is diagrammatically shown amodified form of piston valving, and this illustrated modification isutilized to indicate the two open positions of the valving for flow offluid in opposite directions. Inthese embodiments the piston rod carriesthe piston body 21a and the clamping nut 17, but between the shoulder 18of the piston rod and the inner central portion of the body 21a there isclamped a frusto-conical seating member a which may be economically madeof stamped sheet metal, the upper central annular flange 37 serving toclamp the member in position and the lower outwardly projecting annularflange a providing the inward ledge for the margins of the discs 32. Theoutward depending skirt 28a of the piston provides the upward abutmentfor the valving as in the device shown in FIGURE 2 of the drawings.

If it is found to be necessary or advisable, particularly in the use ofmultiple discs, the frusto-conical inward seating member may be formedas illustrated in FIGURE 5 of the drawings, the element itself beingdesignated 20b and provided with the flanges 37 and 30a as in theearlier described embodiment, but also provided with the verticallyfaced bosses or spurs 40 which ensure the centering of the discs of thestack. However, it should be pointed out that in most cases thesecentering spurs are not absolutely necessary; as a matter of fact,rather remarkably, when there is an initial pre-stress applied to thediscs, they seem to have a tendency to remain centered and even tocenter themselves automatically under the effect of the deformations andsliding contacts which accompany their operation.

In operation, during compression movement of the piston, that is to say,upwardly as viewed in FIGURES 2, 3 and 4, the pressure of fluid abovethe discs 32 serves to flex the discs downwardly at their outer marginsand permit an escape of fluid through the resulting annular passagewaybetween the lower edge of the skirt 28 or 28a as illustrated in FIGURE3.

On the other hand, during expansion movement (or rebound movement in thecase of a vehicular shock absorber) the pressure of fluid beneath thepiston sets upon the stocks of discs to flex their inner margins 31upwardly away from the seat 30 or 30a and provide an annular passageway46 for upward flow or fluid. Thus, there is provided essentially a shockabsorber piston, the operation of which in both directions is providedby a single valve.

The most outstanding feature of this type of valve resides in the factthat not only is each of the valve discs not subject at any of its pivotor fulcrum points to a rigidly clamped fixed-end effect, but the disc iscompletely mobile at all points. If the conditions of the valve discs inFIGURES 3 and 4 are compared, it is seen that between the compressionmovement and the expansion movement, the conically deformed stack offlap valve discs need never to undergo a' reversal of curvature but issubjected substantially to a translatory movement, which justifies theapplication of the designation floating flap valve.

Also, for many reasons, the adjustment of vehicle sus- 4. pension shockabsorbers is generally established with a co-eflicient of braking duringthe expansion or rebound movement which is greater than that of thebraking during compression. One of the main advantages of this newpiston is that it automatically and inherently pro vides an absolutelyspecific ratio between the expansion and the compression braking whenthe angle of the conical surface 50 of the projecting portion 26A of thesupport member 20 has been properly predetermined. This feature has theimportant advantage of simplicity of manufacture and inspection. Byvarying the angle of the surface 59 one can, without modifying thecompression characteristics, stiffen the expansion characteristics asmuch as desired and thus retain positive control of the expansion strokecompression ratio. It will also be clearly understood that due to theinclination of the frusto-conical surface 56, progressive flexing of thediscs results in a small initial volume of liquid but which increases asthe bending of the discs increases.

Furthermore, the characteristics of the expansion and compressionfactors obtained with such a piston prove to be remarkably linear whichis in general an excellent property for a vehicle suspension shockabsorber. However, it is to be noted that the shape of the expansioncurve can be varied as desired by substituting for the conical surface50 a surface of revolution having a curved or linear generatrix ofsuitable profile.

It will thus be understood that the portion of the member 20 above thenormal level of the valve discs 32 and represented by the surface 59,constitutes an obstruction to the free and uninhibited flow of fluidonce it has passed the orifice afforded by the flexing of the innermargin of the valve discs. In certain prior developments of this generalcharacter the nature of the opening between the flexing inner margins ofthe valve disc was such that the fluid was immediately unconfined andnot affording any substantial resistance to the flow of the fluid onceit has passed the lip or margin of the valve disc. In the present case,the surface 5t affords a graduated throttling or restriction to flow incontrast with such prior developments, but at the same time graduallyreducing such resistance according to a linear law.

The initial slight stressing of the discs, already mentioned, may bedetermined by a small difference in level of the lower end of the skirtportion 28 and the upper face of the ledge 30, which should be less thanthe thick ness of the stack of discs. For instance, in a typical shockabsorber installation this distance could be in the neighborhood oftwo-tenths of a millimeter.

The principal operation described above can be supplemented by providingone or more permanent passageways through the piston for thetransmission of fluid during a smooth boulevard ride, when the dampingproperties of the shock absorber need not be brought into severe action.In FIGURE 2 it is indicated that these passageways may take the form ofsmall notches cut in the inner face of the outer wall of the cavity 25,that is to say, in the skirt portion 28. These notches are indicated at52 in the drawings. Similar notches could be cut in the top surface ofthe ledge 30 or through the conical portion of the sheet metal member26a as indicated at 53 in FIGURES 3, 4 and 5 of the drawings.

Such permanent passageways can also furnish the following novel propertywhich has technical advantages; they can be made in a generally conicalor similar shape so as to impart to them also a differential resistanceeffect, for instance greater in expansion than in compression. Thepreferred embodiment will in this case be in the form of the conicalpassageways 55 provided in the supporting member 20 as shown in FIGURE2.

It is understood that various changes and modifications may be made inthe embodiments illustrated and described herein without departing fromthe scope of the invention as determined by the following claims.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

1. In a direct-acting piston-and-cylinder shock absorber, a cylindercontaining damping fluid, a piston disposed for reciprocation therein,means for by-passing damping fluid through the piston from one side tothe other, said means including an annular cavity formed in said pistonand having inner and outer circular walls, at least one thin annularresilient valve disc positioned within said cavity, a fixed annular seaton one wall of said cavity facing in one axial direction and a fixedannular seat on the other of said walls facing in the opposite axialdirection, the outer marginal portion of said disc normally seated inthe axial direction against the seat on the outer one of said walls, andthe inner marginal portion of said disc seated against the seat on theinner one of said walls, whereby movement of said piston in onedirection causes pressure of damping fluid against the valve disc in theopposite direction and causes the disc to yieldably flex away from oneof said seats and afford an annular opening etween the adjacent portionsof the disc and the seat for the controlled passage of fluidtherethrough, characterized by the provision of an obstruction to flowof fluid comprising a part projecting from at least a portion of theperiphery of the support so as to throttle the flow of damping fluidpast this inner portion of the valve disc, and the obstruction soconstructed and arranged as to gradually decrease the throttling effectas the flexing of the disc increases.

2. The shock absorber as set forth in claim 1 in which the internaldiameter of the valve disc is substantially the same as the largerdiameter of the sloping projecting part at the point nearest the seatwhereby the annular valve disc is centered at this point when closed.

3. The device as set forth in claim 1 in which there are disposedprojecting ribs of substantially uniform diameter extending radiallyoutwardly from the inclined surface of the projecting part so as tomaintain the centering of the valve disc in all positions of operation.

4. In a direct-acting piston-and-cylinder shock absorber, a cylindercontaining damping fluid, a piston disposed for reciprocation therein,means for by-passing damping fluid through the piston from one side tothe other, said means including an annular cavity formed in said pistonand having inner and outer circular walls, at least one thin annularresilient valve disc positioned within said cavity, a fixed annularshoulder on one wall of said cavity facing in one axial direction and afixed annular shoulder on the other of said Walls facing in the oppositeaxial direction, the outer marginal portion of said disc normally seatedin the axial direction against the shoulder on the outer one of saidwalls and being unconfined laterally at this point, and the innermarginal portion of said disc seated against the shoulder on the innerone of'said Walls, whereby movement of said piston in one directioncauses pressure of damping fluid against the valve disc in the oppositedirection and causes the disc to yieldably flex away from one of saidshoulders and aiford an annular opening between the adjacent portions ofthe disc and the shoulder for the controlled passage of fluidtherethrough, the outer shoulder and the outer portion of the disc beingthe ones involved in passing the fluid during the compression stroke ofthe piston and the inner shoulder and inner portion of the disc beingthe ones involved during the extension or rebound stroke, and the discscomprising the only movable valve elements carried by said piston, oneof said circular Walls being cut away adjacent the cooperating edgeportion of the disc to afford an opening of variable section as theadjacent edge portion of said disc is flexed.

5. The shock absorber as set forth in claim 4 in which the said innerwall is tapered in that it has a radially outwardly facing surface inthe form of a surface of revolution of a diameter progressivelydecreasing from the level of the valve disc seating shoulder, so as tooffer to the passage of liquid a variable and increasing greater sectiondepending on the degree of flexing of the disc.

6. The shock absorber as set forth in claim 4 in which said inner wallof the cavity is frusto-conical.

7. The shock absorber as set forth in claim 6 in which the annularelement is of sheet metal and the intermediate portion thereof is offrusto-conical configuration.

References Cited by the Examiner UNITED STATES PATENTS 2,670,814 3/54Ball 188-88 FOREIGN PATENTS 969,330 5/58 Germany. 1,065,526 1/54 France.

ARTHUR L. LA POINT, Primary Examiner, EUGENE o. BOTZ, Examiner,

1. IN A DIRECT-ACTING PISTON-AND-CYLINDER SHOCK ABSORBER, A CYLINDERCONTAINING DAMPING FLUID, A PISTON DISPOSED FOR RECIPROCATION THEREIN,MEANS FOR BY-PASSING DAMPING FLUID THROUGH THE PISTON FROM ONE SIDE TOTHE OTHER, SAID MEANS INCLUDING AN ANNULAR CAVITY FORMED IN SAID PISTONAND HAVING INNER AND OUTER CIRCULAR WALLS, AT LEAST ONE THIN ANNULARRESILIENT VALVE DISC POSITIONED WITHIN SAID CAVITY, A FIXED ANNULAR SEATON ONE WALL OF SAID CAVITY FACING IN ONE AXIAL DIRECTION AND A FIXEDANNULAR SEAT ON THE OTHER OF SAID WALLS FACING IN THE OPPOSITE AXIALDIRECTION, THE OUTER MARGINAL PORTION OF SAID DISC NORMALLY SEATED INTHE AXIAL DIRECTION AGAINST THE SEAT ON THE OUTER ONE OF SAID WALLS, ANDTHE INNER MARGINAL PORTION OF SAID DISC SEATED AGAINST THE SEAT ON THEINNER ONE OF SAID WALLS, WHEREBY MOVEMENT OF SAID PISTON IN ONEDIRECTION CAUSES PRESSURE OF DAMPING FLUID AGAINST THE VALVE DISC IN THEOPPOSITE DIRECTION AND CAUSES THE DISC TO YIELDABLY FLEX AWAY FROM ONEOF SADI SEATS AND AFFORD AN ANNULAR OPENING BETWEEN THE ADJACENTPORTIONS OF THE DISC AND THE SEAT FOR THE CONTROLLED PASSAGE OF FLUIDTHERETHROUGH, CHARACTERIZED BY THE PROVISION OF AN OBSTRUCTION TO FLOWOF FLUID COMPRISING A PART PROJECTING FROM AT LEAST A PORTION OF THEPERIPHERY OF THE SUPPORT SO AS TO THROTTLE THE FLOW OF DAMPING FLUIDPAST THIS INNER PORTION OF THE VALVE DISC, AND THE OBSTRUCTION SOCONSTRUCTED AND ARRANGED AS TO GRADUALLY DECREASE THROTTLING EFFECT ASTHE FLEXING OF THE DISC INCREASES.